This application claims the priority of Korean Patent Application No. 10-2003-0039773 filed on Jun. 19, 2003 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus and method operable to detect duplicate Internet Protocol (IP) addresses in a mobile ad hoc network (hereinafter, referred to as “MANET”) environment, and more particularly, to a method of allocating IP addresses and detecting duplicate IP addresses as a single terminal participates in an already established MANET or is disconnected from and reconnected to the already established MANET while transmitting/receiving a Hello packet containing an identifier for identifying each MANET.
2. Description of the Related Art
As a network is constructed with no help of an infrastructure in a MANET environment, it is difficult to use protocols for automatically allocating IP addresses, such as Dynamic Host Configuration Protocol (DHCP) which is used in a wired network. Accordingly, it is required that each terminal itself allocates an IP address and detects duplicate IP addresses.
Operations in the related art are shown in FIGS. 1A and 1B. FIG. 1A is an exemplary view showing the structure of a MANET and an IP address detection method, and FIG. 1B is an exemplary view showing the order of allocation and duplicate detection of IP addresses performed in a conventional terminal.
For connection of terminal A to the MANET consisting of terminal B, terminal C and terminal D, terminal A selects an IP address that it intends to use, and then transmits a duplicate detection-requesting message in a broadcast manner, as shown in FIG. 1B. Terminals B, C and D then check whether the IP address collides with their own IP addresses. If there is no collision, terminals B, C and D do not transmit any messages. If there is a duplicate, terminals B, C and D transmit a duplicate detection message to terminal A that has issued the IP address duplicate detection-requesting message. At this time, if terminal A does not receive any duplicate detection messages for a certain period of time after transmitting the duplicate detection-requesting message, it determines that there is no duplicate and is then connected to the already established MANET.
As a MANET constructed without using infrastructure has not yet been commercialized, it does not have a specific standard function for the automatic allocation of IP addresses. Therefore, the MANET simply transmits its own IP address to peripheral terminals during an initial stage and detects duplicate IP addresses according to responses from the peripheral terminals.
However, since additional messages should be exchanged again if it is detected that an initially allocated IP address has been duplicated, this method may increase the load of the network. Furthermore, since all terminals have mobility, the terminals move among networks and connection or disconnection among networks frequently occurs. Because of this, such a method cannot easily perform the duplicate detection according to the connection or disconnection of a given network. Moreover, wireless packets are more sensitive to packet loss than wired packets. If a duplicate detection packet is lost and a new IP address is allocated, it is difficult to detect it again later. Even though it has been detected again, an IP address related to the duplication affects routing construction information. As a result, an incorrect routing table is formed and an existing connection may thus be disconnected.